I used to “flash” different operating systems IE-Cyanogenmod) on an Android phone. However, I had to sideload apps and they didn’t work properly without a Google account. Also, I assume they work with “Carplay/Android auto”?
It’s been so long I have no idea what ROMs are out there now.
I had mine flashed 5 years ago. Works like charm.
Not everyone can do that is the problem. I went to try that myself a couple times but was afraid I would brick a perfectly fine phone. It is easy to do. And some just cannot be rooted at all without bricking it. Serious homework and direct advice is required to make this happen correctly.